List of astronomical interferometers at visible and infrared wavelengths

Current Performance of Ground-Based Interferometers

Here is a list of currently existing astronomical optical interferometers (i.e. operating from visible to mid-infrared wavelengths), and some parameters describing their performance.

Columns 2-5 determine the range of targets that can be observed and the range of science which can be done. Higher limiting magnitude means that the array can observe fainter sources (and the most interesting sources are often very faint). The limiting magnitude is determined by the atmospheric seeing, the diameters of the telescopes and the light lost in the system. A larger range of baselines means that a wider variety of science can be done and on a wider range of sources.

Columns 6-10 indicate the approximate quality and total amount of science data the array is expected to obtain. This is per year, to account for the average number of cloud-free nights on which each array is operated.

Current Performance of Existing Astronomical Interferometers

Interferometer and observing mode	Waveband	Limiting magnitude	Minimum baseline (m) (un-projected)	Maximum baseline (m)	Approx. no. visibility measurements per year (measurements per night x nights used per year)	Max ratio of no. phase / no. amplitude measurements (measure of imaging performance, 0 = none)	Accuracy of amplitude2 measurements	Accuracy of phase measurements (milli-radians)	Number of spectral channels (max in use simultaneously)	Comments
CHARA Array	V, R, I, J, H, K	8	34	330	7500	0.7	1%	10	30000	Yes... 30000 in the visible band
COAST visible	R, I	7	4	60	2000	0.5	4%	10	4?	300 cloudy nights per year
COAST infrared	J, H	3	4	60	100	0.5	20%	10	1	300 cloudy nights per year
GI2T visible	R, I	5	10	65	2000	0	10%	-	400?	Closed in 2006
IOTA	J, H, K	7	6	30	10000	0.3	2%	10	1?	Integrated optics beam combiner
ISI	N	0	10	50	5000	0.3	1%	1	1000
Keck Interferometer	H, K, L, N	10.3	85	85	1000	0	4%	1	330	Nulling Key Science Underway - No imaging on a single baseline instrument
Keck Aperture Masking	J, H, K, L	2	0.5	9	20000	0.9	20%	10	1
MIRA 1.2	R, I	3	30	30	500	0	10%	-	1
Navy Prototype Optical Interferometer(NPOI) visible	V, R, I	5	5	300	50000	0.7	4%	10	16	at NOFS; pending 4 x 1.8m added apertures
Palomar Testbed Interferometer	J,H,K	7	86	110	50000	0	2%	0.1	5,10	"dual-star" capable , No imaging on a single baseline instrument. Closed 2009.
SUSI	B, V, R, I	5	5	640	5000	0	4%	10	?	No imaging on a single baseline instrument
VLTI +UTs AMBER	J, H, K simultaneously	7	46	130	400	0.3	1%	10	2000	Used for a few weeks per year
VLTI +ATs AMBER	J, H, K simultaneously	4	46	130	400	0.3	1%	10	2000
VLTI +UTs VINCI	K	11	46	130	400	0	>1%	-	1	Integrated optics beam combiner
VLTI +ATs VINCI	K	Never checked	12	200	400	0	>1%	-	1
VLTI +UTs MIDI	N	4.5	46	130	200	0	10%	-	250	Used for a few weeks per year
VLTI +ATs MIDI	N	4.5	?	200	200	0	10%	-	250

New Interferometers and Improvements to Existing Interferometers

Expected Future Performance of Astronomical Interferometers

Interferometer and observing mode	Waveband	Limiting magnitude	Minimum baseline (m) (un-projected)	Maximum baseline (m)	Approx. no. visibility measurements per year (measurements per night x nights used per year)	Max ratio of no. phase / no. amplitude measurements (measure of imaging performance, 0 = none)	Accuracy of amplitude2 measurements	Accuracy of phase measurements (milli-radians)	Number of spectral channels (max in use simultaneously)	Comments
LBTI (near infrared)	J, H, K	>20	0	22	10000000	1	30%	100	100?	2006?
MRO	R, I, J, H, K	14	7	400	100000	0.6	1%	10	1000?	Under Construction
VLTI (near infrared using 4 ATs and PRIMA)	J, H, K	12	8	200	10000	1	1%	0.1	4000?	Operating every night 2008?
VLTI (near infrared using 3 UTs and PRIMA)	J, H, K	14	46	130	500	1	1%	0.3	4000?	2008?

See also

• Photometric system has a key for waveband letters.

Further reading

• Fujinobu Takahashi (2000). Very long baseline interferometer. IOS Press. ISBN 4274903788. http://books.google.com/?id=tEUAtdhpXBMC.